Many scientists contend that release of refrigerants into the atmosphere deleteriously affects the ozone layer that surrounds and protects the earth from ultraviolet solar radiation. Recent international discussions and treaties, coupled with related regulations and legislation, have renewed interest in devices for recovery and storage of used refrigerant from refrigeration equipment for later purification and reuse, or for proper disposal. U.S. Pat. No. 4,261,178, assigned to the assignee hereof, discloses a refrigerant recovery system in which the inlet of a compressor is coupled through an evaporator and through a manual valve to the refrigeration equipment from which refrigerant is to be recovered. The compressor outlet is connected through a condenser to a refrigerant storage container or tank. The condenser and evaporator are combined in a single assembly through which cooling air is circulated by a fan. Content of the storage container is monitored by a scale upon which the container is mounted for sensing weight of liquid refrigerant in the container, and by a pressure switch coupled to the fluid conduit between the condenser and the container for sensing vapor pressure within the storage container. A full-container condition sensed at the scale or a high-pressure condition sensed at the pressure switch terminates operation of the compressor motor. A vacuum switch is positioned between the inlet valve and the evaporator for sensing evacuation of refrigerant from the refrigeration equipment and automatically terminating operation of the compressor motor.
U.S. Pat. No. 4,768,347, also assigned to the assignee hereof, discloses a refrigerant recovery system that includes a compressor having an inlet coupled through an evaporator and through a solenoid valve to the refrigeration equipment from which refrigerant is to be recovered, and an outlet coupled through a condenser to a refrigerant storage container or tank. An impending tank overfill switch, comprising a tank scale limit switch and/or a tank pressure sensor switch, is connected across utility power to enable operation of the inlet solenoid valve and/or the compressor when the container is not full, and to prevent or terminate application of power when the container becomes full.
Although the systems disclosed in the noted patents address and overcome problems theretofore extant in the art, further improvements remain desirable. For example, it is desirable in many applications to provide for connection of the recovery system to multiple storage containers, which conventionally come in standard sizes such as thirty and fifty pound containers. Desirably, impending overfill of a container would automatically result in the feeding of refrigerant to another container until all containers become full. In this way, the operator may concentrate on refrigerant recovery and equipment repair, without requiring disconnection and replacement of storage containers during a recovery operation. It is a general object of the present invention to provide a refrigerant recovery system and method that satisfies these objectives.